It's an interesting comparo, and should be usable for some real credit in advertising, but the truth is this has been done before (as others have indicated) and seemingly hasn't amounted to much positive benefit for GM. This is the segment in the pickup market where GM seems to be having the most difficulty getting any real traction, and yet I would argue that in many ways it is the area where they are arguably the most competitive with Ford and Ram. I've blamed part of this struggle to find greater success on the lack of a SFA in 4x4 models in the past, an issue which I think poisons the whole HD well for GM to some degree even if it doesn't apply directly to 2wd models. Still, I'm not sure that explains it all. And now a new Ford SD pickup is coming, which can't be considered a plus if they can't even gain any real traction against the existing model which uses a cab design from the paleolithic era.
In contrast to the chest pounding that is taking place in threads where the new Expy/Nav twins are compared to the better selling GM suv's I think this is an area where you have to do the opposite and start asking how GM can put forth so much effort and manage so little headway against Ford and Ram here. Guesses off the top of my head include......
1: Lack of a SFA in 4x4 models (as mentioned above)
2: People know that the otherwise excellent Duramax is an Isuzu-designed piece and in this somewhat macho category where people love baseball, mom, and apple pie that can't really be seen as a plus
3: Possible fallout for some recent (last decade) political decisions related to GM, this seems like a segment that would suffer more than some, but I would still think this relatively minor by this point
Other than that I've got nothing.